Drop bottom mine car



April 11, 1950 T. E. BOWEN 2,503,706

DROP BOTTOM MINE CAR Filed March l2, 1949 4 Sheets-Sheet 1 24 .7w 6. BWW W, W

IN V EN TOR. 55

April 11, 1950 T. E. BOWEN DROP BOTTOM MINE CAR Filed March 12, 1949 4 Sheets-Sheet 2 INVENTOR.

BY WW arrow/v5) April 11, 1950 Y T. E. BOWEN 2,503,706

DROP BOTTIOM MINE CAR Filed March 12, 1949 4 Sheets$heet 3 15 f I 2L 52 k 10 102 if?! m 1 m! \n fiflwa ml J1) Wil W" 1: 72 11 in M 6 I. \\1 mrn-1 J 1; u W" W W a m m m l l V l 5N1 Wl l 74 r 69 I W f 14 TTOTNE Y April 11, 1950 T. E. BOWEN DROP BOTTOM MINE CAR Filed March 12, 1949 4 Sheets-Sheet 4 INVENTOR.

flTTORNEY open it.

atented Apr. 11 195 DROP BOTTOM MINE CAR Thomas Earl liiowen, Birmingham, Ala, assigno'i' to Empire Industries, Inc., New York, N.- Y., .a

corporation of Delaware Application March 12, 1949, Serial No. 81,145

7 Claims. (Cl. Min-25.3)

This invention relates to mine cars and more particularly to the type known as drop bottom cars.

It is an object of the invention to provide a drop bottom mine car which is automatic in operation wherein thebottomdoors are hinged at their forward ends, the fore door being mounted on a hinge rod rotatable in the side sills and the aft door being mounted on a hinge rod having journals rotatable in bearings which are inturn rotatable and movable longitudinally relative to the side sills whereby friction between the operating parts is reduced to a minimum. When the doors are in closed position the rear end of the aft door is held closed by a latch, the forward end of the aft door then providing an abutment upon which the rear end of the fore door rests to keep it closed. When the latch is released, the aft door swings downwardly on its hinge rod and meantime during this opening movement of the aft door, the aft door moves backward bodily on the frame to remove the abutment upon which the rear end of the fore doorwas resting thereby causing the fore door to swing downwardly to Although the novel features which are believed to be characteristic of the invention will be pointed out in the annexed claims, the invention itself as to its objects and advantages and the manner in whlch it may be carried out may be-better understood by reference to the follow-- ing description taken in connection with the accompan-ying drawings forming apart hereof, in

which a Fig. l is a top plan view of the bin orbed of the car partly broken away;

Fig. 2 is a view in elevation on line 2-4 of i Fig. 3 is a view in elevation looking toward the rear end of the car on line 3--3 of Fig. 2 and partl-y broken away to show the latching arrangement for the aft door;

Fig. 4 is an end view .of the car in elevation looking toward'the rear end;

Fig. 5 is a plan view on line v5---.'i of Fig. 2 with part of the fore door broken away;

Fig. .6 is a side view in elevation of the car partly broken away and showing the fore door in up position and the aft door prior to final closing;

Fig. .7 is a view to smaller scale showing the mine car at atipple with both doorsopen;

Fig. 8 is a view-in elevation showing a modified form of the rear-door hinge mounting; an

Fig. 9 is a viewat right angles to. Fig. 8.

5 Referring now to the drawings, in which like 2 reference characters denote like parts throughout the several views, the car comprises a main frame consisting of side sills l0 and II and end sills l2 and i3 fastened together in the usual way as by welding, or riveting as known in the art. The sills are of standard structural steel channel members of suitable size and strength. The frame is mounted on wheels H, l5, l6, I! carried on the axles l8, 19 extending through apertures in the webs of the side sill channel members H), H and supported in axle boxes 20, 21, 22, 23 whichmay be of known design. I

The frame carries a bed consisting of side walls 24 and 25, end Walls 26 and 21, and the doors 28 and 29 which provide a bottom for the bed of the car. As shown, side walls 24 and have a vertical portion 30 and 3| and an inclined portion 32 and 33 terminating in a vertical portion 34 and 35 flush with the vertical web portions of the side Sills ill and II. The end walls 26 and 21, as shown, have vertical portions 36 and 3'! and inclined portions 38 and 39 which extend over the axles l8 and Hi. The bed is suitably reinforced by angle irons 41 transverse of the car bed and otherwise as may be desired. It will be manifest that the car frame lends itself to other types of bed side walls and end walls, the selection being frequently governed by the particular conditions existing at a particular mine, as to height, tracks, clearances, and other factors to be reckoned with.

The fore door 28 of the bottom is mounted between the side'sills Ill and II. This door at its forward end is secured to a hinge rod 40. The hinge rod is mounted to rotate on its axis in holes 4| and 42 in the'vertical webs of the-side sills (see Fig. 5), it being noted that the holes eX- tend through reinforcing plates .43 and 44 welded to the side sills. Cotter pins 45 and 46 in the hinge rod maintain it in place for rotation in the holes 4| and 42 which provide bearings in which the rod is rotatable. When not held up in closed position as shown in Fig. 2, the .fore door 28 is free to swing downwardly on the pivot provided by he hinge rod Ml as indicated in dot-dash lines 28a. It will be observed that the fore door 28 has a downwardly inclined portion 50 at its front end, a flat bottom portion 5| in the middlaand at its rear end an upwardly inclined portion 52. It is reinforced by vertical side plates 53 and 54 and a vertical center plate 55.

The aft door 29 is of substantially the same shape as the fore'door, having its forward end secured to a hinge rod 5.6 mounted transverse of the car. It has similar reinforcing side plates 3 and 58 and center plate 59, as does the fore door. It likewise has an inclined portion 66 at its forward end, a flat portion 6! in the middle, an inclined portion 62 and a flat rear portion 63. However, the aft door hinge rod 56 is mounted differently from the fore door hinge rod 46 as described more in detail hereinafter. The fiat rear end portion 63 of the aft door 29 has a rearwardly extending pin 64 secured at the center of the door to cooperate with a latch mechanism designated generally by reference numeral 65. The rear end of the aft door 29 is cut away at the corners as shown at 66, 61. It has a pin 68 secured to the bottom of the door portion 63 and parallel with the end of the door, this pin providing a stub shaft upon which is mounted a cam roller 69 for rotation on this shaft. This roller, as will be described hereinafter, engages and rolls on an upwardly and forwardly inclined wedge I6 which is secured to the frame. The Wedge provides a cam face II so that when the roller rolls up the cam face II it forces the aft door 29 forward relatively to the frame of the car. Although only one such roller and wedge is shown, a like arrangement can be provided at the cut out portion 6'! at the opposite corner so as to provide two rolls and wedges if desired.

; The latch mechanism 65 .comprises a latch member I2 mounted, for pivotal movement about a pivot pin I3. The pivot pin 73 is mounted in a bracket 14 secured to the web of end sill channel iron I3 and hence is held in fixed position on the frame of the car. The pivoted latch member 12 has a cut out portion providing an inclined cam face I5 which engages a pin 16 fixed to a lever bar 11. The lever bar ll is pivoted at its end on a pivet pin I6 secured to a vertical angle iron 19 which is Welded to the frame and bed. The lever bar 71 extends through a slot in the web 86 of angle iron 19 and through a slot in the web SI of a similar angle iron 82 on the other side of the-rear end of the car. The lever arm 'I'! has a short downwardly bent portion 83 extending be- ;yond the left rear wheel 56 of the car, to engage a trip cam 86 (see Fig. 7) which may be placed at a desirable place along the track 85 in which the car or a train of cars operates. The lever bar pin I6 is vertically slidable in a guide slot 86 provided in a vertical plate ti -secured at its upper end to the bed of the car and at itslower end to the end sill I3.

The pivoted latch member I2 below its pivot I3 has a notch 88 providing a, shoulder 89 upon which the door pin 64 can rest to maintain the aft door 29 in its up or closed position. Beneath the shoulder 89 is an inclined cam face 96. It .may engage the door pin 64 when the aft door 29 jis raised from its down or open position to its :up or closed position.

A yieldable helical spring 9I secured to the upper end of the latch member :12 and to the bed normally urges the latch member in a counterclockwise direction about pivot :13 as Viewed in Fig. 3.

The center hinge rod 56 is mounted for rota.-

of the door 29. is bent around the hinge rod 56 forming a loop 99. The loop may be formed so that the hinge rod'rotates in it or it may be formed so that the hinge rod is fixed to it so that it does not rotate in the loop. Likewise the for- Ward end portion of door 28 has a loop 95 which 4 may be mounted in similar fashion on hinge rod 46.

The ends of hinge rod 56 extend through elongate guide slots 96 and 91 (see Fig. 5) in the webs of side sills I6 and II. The slots are similar and are inclined downward toward the rear as shown in Fig. 2. Reinforcing plates 96 and 99 (see Fig. 5) having slots registering with the slots in the side sills are provided to strengthen the side sills because of the cutting away of the webs to form the slots. Mounted for rotation on each end of the hinge rod 56 is a hinge rod roller 469 and IN. These rollers may roll on plates forming guide tracks I62 and I63 which are secured to the reinforcing plates 98 and 99. The trackways are mounted parallel with the slots 96 and 97. The hinge rod is rotatable in the rollers; thus the rollers I66 and I6I provide bearings which themselves are movable longitudinally of the frame when the hinge rod 56 is moved bodily in the slots, since the rollers I66 and I6I roll on the trackways I62 and I63.

It will be observed that when the fore door 28 is in up or closed position and the aft door 29 is in up or closed position as shown in Fig. 2,

the aft door is forward in the guide slots 96 and 91 and the loop 94 of the aft door provides a stop or rest on which the rear end of the fore door 28 rests to maintain the fore door in closed position. The aft door 29 is maintained in forward position by the wedge 16 and in up or closed position by pin 64 which restson shoulder 89 of the latch member I2.

When the latch member I2 is actuated by lifting the lever rod 11, the latch member is rotated in clockwise direction asviewed in Fig. 3 and this removes the shoulder 89 from under the pin 64 permitting the rear end of door 29 to fall. This movement of latch member I2 is brought about because pin I6 of the lever bar engages cam face '15 and when the pin I6 of the lever is raised in the slot 86 the latch member 12 is rotated on pivot pin I3 to move shoulder 89 out from under the pin 64.

The car operates as follows. It may be assumed the doors 28 and 29 are in closed position as shown in Fig. 2 and loaded with coal. The car moves on tracks in the direction of the arrow (see Fig. '7). When the rear end of the car passes the trip cam 84 which may be placed along the track, the outer end 83 of lever bar 'II engages the cam 84 and is raised to rotate lever arm TI on its pivot I8. This causes the latch member 12 to rotate on its pivot 73 to withdraw the shoulder 89 from beneath pin 64 of the aft door 29. The weight of the coal will cause door 29 to swing down, about the axis of hinge rod 56. In the meantime the downward movement of the rear end of door 29 permits the door to move bodily toward the rear, the roller 69 rolling on cam face II of wedge I6. The hinge rod 56 moves rearwardly relative to the side sills in slots 96 and 91, the hinge rod rollers I66 and I6I rolling rearwardly on the trackways I62 and I63. Upon this rearward movement of the hinge rod 56, the loop 94 upon which the rear end of door 28 was resting is removed from beneath the door 28, whereupon this fore door swings downwardly about the axis of its hinge rod 46. The trip cam 84 will, of course, be set to release the doors to dump the coal at the tipple I65 and the doors '28 and 29 will hang as shown in Fig. 7.

As the car moves forward, the fore door engages a cam section I66 located between the tracks. A friction late I6! on the fore door is such-that as the car "moves forward the door 28 is swung upwardly on hinge rod 40 so that its rear end is sufliciently high to permit the loop .94 to move in under it. When the aft door reaches the cam section I06 its friction plate I08 engages the cam and the rear :door 'is raised. When it :is swung up sufliciently high for the rol- .ler B8 to engage the wedge 10 the aft door 29 is forced forwardly and when the roller reaches the upper end of the cam face II the hinge rod 56 has moved forward in the .slots 96 and 9'! so that the loop '94 is beneath the rear end of the fore door. In its upward swing movement the pin 64 engages the cam face 90 of the latch memher 12 causing it to rotate on its pivot against the force of yielding spring 9| :and finally the spring 9| causes the latch member to return when the pin 64 is opposite the notch 88 and the shoulder 89 moves in under pin 64 to maintain it and the door 29 in up or closed position. Meantime the car passes track 'cam section 1'06 and the bottom doors remain closed until they are again tripped by raising lever bar 11..

A modified form for mounting the aft door hinge rod is shown in Figs. 8 and 9. In this modified form the aft door 29a which is like door 29 of the form shown in Figs. 1-7, is mounted on hinge rod 56a in the same way as described hereinbefore. This center hinge rod 56a for the aft door extends through arcuate slots 91a, it being understood that each side sill has :a similar ar- 'rangement. It is deemed therefore to be sufficient to describe only :one, as shown .in Figs. 8 and 9. The side .sill Ila is reinforced with a plate 99a. which has an arcuate slot registering with the slot in the web of the side sill. Beheath the slot and substantially parallel thereto and secured "to plate 98a is trackway plate having an arcuate trackway 10 3a upon which the hinge rod roller lflla rolls. The roller lllia is like roller I00 shown in Figs. 1-7. The hinge rod at its end outside the roller [Illa is mounted on a hinge rod link Ililla which has a bore :at its lower end in which the hinge rod 56a is 1110- tatab'ly mounted. The hinge'rod is held in place as 'by =-a cotter pin 2a. The upper end of this link 0a is pivotally mounted on a stud bolt "H l a which is secured to the reinforcing plate 89a; a spacer H2a being provided to keep the link lined up with the outside of roller Mia. The link 110a and trackway l03a is (so arranged that when the hinge rod 56a is moved backward in the door-opening operation, the hinge irod swings on the pivoted link Hlla. and the roller m l-u rolls backwardly ion the-downwardly inoli-n'ed arcuate trackway [0311. .And when the aft door is closed the reverse movement takes place; that is, *the hinge rod 56a 'then moves forward by swinging on the pivoted link Ulla. :to the forward end of the slot 81a while the roller moves forward along trackway 103a. Thus the weight :of the :door is nicely distributed. It will be un ad'erstood as mentioned above that both "ends of hinge rod 56a are arranged in thesame way'and aopera te in similar fashion. noted that this arrangement is such that the "forwvard-end of aft door 29a forms :an abutment for the fore door in similar manner :as the :form shown in Figs. 1-! and is removed from :under the rear 'end of the .fore door in similar fashion. The terms and expressions which have been employed herein are used as terms of description and not .of :limitation and there is I10 intentlon fin-th use 10f such terms and expressions so'f excluding any equivalent "of the features shown Also, may be and described or portions thereof, but it is recognized that various "modifications are possible within thescope of invention claimed.

What claimed is:

1. A :drop bottom mine car which comprises side sill members and end sill members providing a frame, axles :and wheels. carrying said frame, a plurality of drop bottom doors including a fore and an aft door pivotaliy mounted in tandem between said side sills and forming :a bottom for said car, a rotatable fore door hinge rod mounted transverse of the side sill members, "the. forward .end of the fore door being secured thereto, a rotatable aft door hinge rod transverse of the side sill members, the forward end of the aft door being secured thereto, a roller mounted on each end of said aft door hinge rod, a trackway on each side sill providing means tor rolling movement of said rollers back and forth a limited distance relative to said side sills, latch mechanism on said frame for maintaining said aft door in closed position and for releasing said aft door whereby it will open by downward swinging movement about the axis of its hinge rod, wedge means on said frame for engaging the aft door at its rear end to force said door to move forward bodily on said rollers-so that its forward end provides a rest for the rear end of the adjacent fore'door to maintain said fore door in closed position, said aft door :moving 'rearwardly and bodily when said aft door swings downwardiy upon release of said latch mechanism thereby Withdrawing said rest from beneath said fore door thereby causing said for door "to open by swinging downwardly about the axis of its hinge rod and said aft door moving forwardly and'bodily when said aft door swings upwardly to closed position whereby the forward end of the rear door forms a rest for the rear end of the fore door when said fore door is in closed position.

2. A drop bottom mine car which comprises a pair of side sill members and end sill members providing a frame, side and end walls carried on the frame, a fore door and an aft door in tandem between said side sills, a rotatable fore door hinge rod mounted transverse of said side sills and having the forward end of said fore door secured thereto, said hinge rod providing a pivot mounting about which said "fore door may swing downward for opening, a rotatable aft door hinge rod mounted transverse of said side sills and having the forward end of said aft door secured thereto, a roller mounted on each end of said aft door hinge rod, a trackway on each side sill providing means for rolling mo e ment of said rollers thereon a limited distance back and forth along said frame, said aft door hinge rod, rollers, and trackways providing pivot "mountingmeans whereby said aftdoor mayswing downwardly about its hinge rod :axis during opening movement and whereby said aft doorhin'e'e rod moves backward on the frame during the opening movement and forward on the frame during the closing movement; of said raft door,

the forward end of said aft door providing :a rest upon which the rear .end of said fore door restsw'hen the fore door isin closed-position and said aft door hinge rod :is in forward position, wedge means on said frame to engage said aft :door and force it and its j-hinge rod to forward position iduring'the closing movement of said aft :door so that its forward end .is under the rear end of the-fore door when the fore door is swung up to closed position, .latch mechanism operative to hold said aft door in blosed position and to.

release saida'ft-door'for opening, said aft door on itsopening movement swinging downwardly about the axis of its hinge rod and its said hinge rod moving backwardly along said frame thereby removing said rest, from beneath said fore door for opening said fore door.

3. A drop bottom mine car which comprises a pair of side sill members and end sill members providing a frame, a fore door andan aft door in tandem between said side sills, a rotatable fore door hinge rod mounted transverse of said side sills and having the forward end of said fore door secured thereto, said hinge rod providing a pivot mounting about which said fore door may swing downward for. opening, a rotatable aft door hinge rod mounted transverse of said side $1115 with its ends extending through elongate slots in said side sill members and having, the forward end of said aft door. secured thereto, a roller mounted on each end of said aft door hinge rod, a trackway on each side sill adjacent its elongate slot providing means for rolling movement of said rollers thereon a limited distance back and forth along said frame, said aft door hinge rod, rollers, and trackways providing means whereby said aft door may swing downwardly about its hinge rod axis during opening movement and whereby said aft door hinge rod moves backward on the frame within said slots during the opening movement and forward on :2;

the frame within said slots during the closing movement of said aft door, the forward end of said aft door providing a rest upon which the rear end of said fore door rests when the fore door is in closed position and said aft door hinge y;

rod is in forward position in said slots, wedge means on said frame to engage said aft door and force it and its hinge rod to forward position in said slots during the closing movement of said aft door so that its forward end is under the rear end of the fore door when the fore door is swung up to closed position, latch mechanism operative to hold said aft door in closed position and to release said aft door for opening, said aft door on its opening movement swinging downwardly about the axis of its hinge rod and its said hinge rod moving backwardly in said slots along said frame thereby removing said rest from beneath said fore door for opening said fore door.

4. A drop bottom mine car which comprises a pair of side sill members and end sill members providing a frame, a fore door and an aft door in tandem between said side sills, a rotatable fore door hinge rod mounted transverse of said side sills and having the forward end of said fore door secured thereto, said hinge rod providing a pivot mounting about which said fore door may swing downward for opening, a rotatable aft door hinge rod mounted transverse of said side sills with its ends extending through elongate slots in said side sill members which slots are downwardly inclined toward the rear, said aft door hinge rod having the forward end of said aft door secured thereto, a roller mounted on each end of said aft door hinge rod outside said side sill members, a trackway on each side sill memher under and outside said side sill members and providing means for rolling movement of said rollers thereon a limited distance back and forth along said frame, said aft door hinge rod, rollers,

"and trackways providing means whereby said aft door may swing downwardly about its hinge rod axis during opening movement and wh'ereby said aft door hinge rod moves backward on the frame within said inclined slots during't he opening movement and forward on the frame within said inclined slots during the closing movement of said aft door, the forward end of said aft door providing a rest upon which the rear end of said fore door rests when the fore door is in closed position and said aft door hinge rod is in forward position within said inclined slots, wedge means on said frame to engage said aft door and force it and its hinge rod to forward position within said inclined slots durin the closing movement of said aft door so that its forward end is under the rear end of the fore door when the fore door is swung up to closed position, latch mechanism operative to hold said aft door in closed position and to release said aft door for opening, said aft door on its opening movement swinging downwardly about the axis ofits hinge rod and its said hinge rod moving backwardly and downwardly within said inclined slots along said frame thereby removing said rest from beneath said fore door for opening said fore door.

5. A drop bottom mine car which comprises a pair of side sill members and end sill members roviding a. frame, a fore door and an aft door in tandem between said side sills, a rotatable fore door hinge rod mounted transverse of said side sills and having the forward end of said fore door secured thereto, said hinge rod providing a pivot mounting about which said fore door may swing downward for opening, a rotatable aft door hinge rod mounted transverse of said side sills and having the forward end of said aft door secured thereto, a roller mounted on each end of said aft door hinge rod, a trackway on each side sill providing means for rolling movement of said rollers thereon a limited distance back and forth along said frame, said aft door hinge rod, rollers, and trackways providing means whereby said aft door may swing downwardly about its hinge rod axis during opening movement and whereby said aft door hinge rod moves backward on the frame during the opening movement and forward on the frame during the closing movement of said aft door, the forward end of said aft door providing a rest upon which the rear end of said fore door rests when the fore door is in closed position and said aft door hinge rod is in forward position, a. roller mounted for rotation on the rear end of said aft door, wedge means on said frame to engage said roller on the aft door and force said aft door and its hinge rod to forward position during the closing movement of said aft door so that its forward end is under the rear end of the fore door when the fore door is swung up to closed position, latch mechanism operative to hold said aft door in closed position and to release said aft door for opening, said aft door on its opening movement swinging downwardly about the axis of its hinge rod and its said hinge rod moving backwardly along said frame thereby removing said rest from beneath said fore door for opening said fore door.

6. A drop bottom mine car which comprises a pairof side sill members and end sill members providing a frame, a fore door and an aft door in tandem between said side sills, a rotatable fore door hinge rod mounted transverse of said side sills and having the forward end of said fore door secured thereto, said hinge rod providing a pivot mounting about which said fore door may swing downward for opening, a rotatable aft door hingerod mounted transverse of said side sills and extending through elongate slots in each side sill member, said hinge rod having the forward end of said aft door secured thereto, a roller mounted for rotation on each end of said aftdoor hinge rod, a trackway on each side;- ;.sill member adjacent said slots providing means'for rolling movement of said rollers thereon a 'limited distance back and forth along said 1 frame, said hinge rod, rollers, and trackways providingmeans whereby said aft door may swing downwardly about its hinge rod axis during opening zmovement and whereby said aft door hinge rod moves backward on the frame within saidifslots: during the opening movement and forward" on th'eijframe within said slots during the closing-movement of said aft door, the forward end ofsai a'ft door providing a rest upon which the rear fend; of said fore door rests when the fore door: lain closed position and said aft door hinge rod' is in forward position within said slots, a stub shaft mounted on said frame parallel with its end, a-cam roller mounted on said stub shaft for notation, wedge means having a cam face on said framoto engage said cam roller and force said aft door and its hinge rod to forward position duringthe closing movement of said aft door so that its forward end is under the rear end of thegf'foredoor when the fore door is swung up to losed ,-position, latch mechanism operative to hold said aft door in closed position and to release said aftdoor for opening, said aft door on its opgning'movement swinging downwardly about the ,axis of,..:its hinge rod and its said hinge rod moving backwardly within said slots along said frame thereby removing said rest from beneath said fore door for opening said fore door. if

7. A drop bottom mine car which comprises a pair of side sill members and end sili members providing a frame, a fore door'f-fand a n aft door in tandem between said side sills,' a'-'rotatable fore door hinge rod mounted transverseV-of-said side sills and having the forward end of said fore door secured thereto, said hinge rod providing a Divot mounting about which said foredoor may swing .i l o 9 8' $39 {1 1' h rod mounted transverse of said side sills and extending through elongate slots in each side sill member, said hinge rod-having the forward end of said aft door secured thereto, a link on each side sill pivoted at itsupper end for swinging movement and having a bore at its lower end, the ends of said aft door hinge rod being mounted for rotation in said bores of said links, a roller mounted for rotation on each end of said aft door hinge rod, a trackway on each side sill member adjacent said slots providing means for rolling movement of -said rollers thereon a limited distance back and'forth along said frame, said hinge rod, link, rollers,iand trackways providing means whereby said aft door may swing downwardly about its hinge-god axis during opening movement and whereby said aft door hinge rod moves backward on the frame within said slots during the opening movement and forward on the frame within said slots during the closing movement of said aft door, the forward end of said aft door providing a rest upon which the rear end of said fore door restswhen the fore door is in closed position and said; aft door hinge rod is in forward position within, said slots, a stub shaft mounted on said-frame. parallel with its end, a cam roller mounted on said stub shaft for rotation, wedge means having a cam face on said frame to engage said cam roller and force said aft door and its hinge rod to forward position during the closing movement of said aft door so that its forward end is under the rear end of the fore door when the fore door is swung up to closed position, latch mechanism operative to hold said aft door in closed position and to release said aft door for opening, said aft door on its opening movement swinging downwardly about the axis of its hinge rod and its said hinge rod moving backwardl within said slots along said frame thereby removing said rest from beneath said fore door for opening said fore door.

' THOMAS EARL BOWEN.

No references cited. 

